def test_function(x, t, c):
    return 2 * sin(pi * x) * (
            -2 * pi * c * (1 + 1j * t ^ 2) * (t ^ 4 + 1) * sin(2 * pi * x) - pi ^ 2 * (t ^ 2 - 1j) + 2 * 1j * t)